The retention rate (RR) is a measure currently used by officers of the Deputy Chief of Naval Operations (Manpower, Personnel, and Training) (OP-01) to assess the Navy's ability to build and maintain a career force of officers. This rate employs the minimum service requirement (MSR) as a point of reference. However, since the MSR frequently does not reflect an officer's true obligation, the RR tends to be overstated. As a result, the maintainability of the career force is overstated. This report describes the base force retention rate (BFR), an alternative to the RR. The BFR does not rely on MSR-based computation but, rather, is the proportion of officers between 5 and 10 years of service who resign their commission annually. The report includes illustrations of the BFR's usefulness in identifying changes or trends in an officer community's retention behavior--trends that the conventional RR might not reveal or might only uncover much later than would the BFR.